--- a/src/names.lisp Thu Jan 26 23:53:51 2017 +0000
+++ b/src/names.lisp Tue Jan 31 18:54:39 2017 +0000
@@ -85,3 +85,4 @@
(Lu cia nia)
(Da niela)
(Ga brie la))
+
--- a/src/random-numbers.lisp Thu Jan 26 23:53:51 2017 +0000
+++ b/src/random-numbers.lisp Tue Jan 31 18:54:39 2017 +0000
@@ -154,5 +154,147 @@
(first (random-weighted-list weights 1)))
+;; from cl-utilities
+
+;; If we're using the SB-ROTATE-BYTE extension, we should inline our
+;; call and let SBCL handle optimization from there.
+#+sbcl (declaim (inline rotate-byte))
+
+(defun rotate-byte (count bytespec integer)
+ "Rotates a field of bits within INTEGER; specifically, returns an
+integer that contains the bits of INTEGER rotated COUNT times
+leftwards within the byte specified by BYTESPEC, and elsewhere
+contains the bits of INTEGER. See http://www.cliki.net/ROTATE-BYTE"
+ (declare (optimize (speed 3) (safety 0) (space 0) (debug 1)))
+ #-sbcl
+ (let ((size (byte-size bytespec)))
+ (when (= size 0)
+ (return-from rotate-byte integer))
+ (let ((count (mod count size)))
+ (flet ((rotate-byte-from-0 (count size integer)
+ (let ((bytespec (byte size 0)))
+ (if (> count 0)
+ (logior (ldb bytespec (ash integer count))
+ (ldb bytespec (ash integer (- count size))))
+ (logior (ldb bytespec (ash integer count))
+ (ldb bytespec (ash integer (+ count size))))))))
+ (dpb (rotate-byte-from-0 count size (ldb bytespec integer))
+ bytespec
+ integer))))
+ ;; On SBCL, we use the SB-ROTATE-BYTE extension.
+ #+sbcl (sb-rotate-byte:rotate-byte count bytespec integer))
+
+
+;;;; PCG
+(defstruct (pcg (:constructor make-pcg%))
+ (state 0 :type (unsigned-byte 64))
+ (increment 0 :type (unsigned-byte 64)))
+
+(declaim (inline permute-xor-shift permute-rotate advance-state))
+
+(defun permute-xor-shift (data)
+ (declare (optimize (speed 3) (debug 0) (safety 1))
+ (type (unsigned-byte 37) data))
+ (-<> data
+ (ash <> -18)
+ (logxor data <>)
+ (ldb (byte 32 0) <>)))
+
+(defun permute-rotate (data selector)
+ (declare (optimize (speed 3) (debug 0) (safety 1))
+ (type (unsigned-byte 32) data)
+ (type (unsigned-byte 5) selector))
+ (sb-rotate-byte:rotate-byte selector
+ (byte 32 0)
+ data))
+
+(defun advance-state (pcg)
+ (declare (optimize (speed 3) (debug 0) (safety 1))
+ (type pcg pcg))
+ (setf (pcg-state pcg)
+ (mod (+ (* (pcg-state pcg) 6364136223846793005)
+ (pcg-increment pcg))
+ (expt 2 64)))
+ nil)
+
+
+; uint64_t oldstate = rng->state;
+; rng->state = oldstate * 6364136223846793005ULL + rng->inc;
+; bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+; >>27
+; bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb...........................
+; assign to uint32 fuckin lol
+; .....bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb...........................
+
+; uint32_t xorshifted = ((oldstate >> 18u) ^ oldstate) >> 27u;
+; uint32_t rot = oldstate >> 59u;
+; return (xorshifted >> rot) | (xorshifted << ((-rot) & 31));
+(declaim (ftype (function (pcg) (unsigned-byte 32)) pcg))
+
+(defun-inlineable pcg-random (pcg)
+ (declare (optimize (speed 3) (debug 0) (safety 1))
+ (type pcg pcg))
+ (let* ((state (pcg-state pcg))
+ (data (ldb (byte 37 (- 64 37)) state))
+ (selector (ldb (byte 5 (- 64 5)) state)))
+ (advance-state pcg)
+ (-<> data
+ (permute-xor-shift <>)
+ (permute-rotate <> selector))))
+
+(defun make-pcg (seed &optional (stream-id 0))
+ (let* ((increment (logior 1 (ash stream-id 1)))
+ (pcg (make-pcg% :state 0 :increment increment)))
+ (pcg-random pcg)
+ (incf (pcg-state pcg) seed)
+ (modf (pcg-state pcg) 64)
+ (pcg-random pcg)
+ pcg))
+
+(defun pcg-random-bounded (pcg bound)
+ (declare
+ (optimize (speed 3) (debug 0) (safety 1))
+ (type pcg pcg)
+ (type (and (unsigned-byte 32)
+ (integer 1))
+ bound)
+ (inline pcg-random))
+ (loop
+ :with threshold = (mod (expt 2 32) bound)
+ :for n = (pcg-random pcg)
+ :when (>= n threshold)
+ :do (return (values (mod n bound)))))
+
+(declaim (ftype (function (pcg (integer 1 32))
+ (unsigned-byte 32)) pcg-random-bits))
+
+(defun-inline pcg-random-bits (pcg count)
+ (declare (optimize (speed 3) (debug 0) (safety 1))
+ (inline pcg-random))
+ (ldb (byte count 0) (pcg-random pcg)))
+
+(defun pcg-random-float (pcg)
+ (declare (optimize (speed 3) (debug 0) (safety 1))
+ (type pcg pcg))
+ ; https://en.wikipedia.org/wiki/Single-precision_floating-point_format
+ ; Singles have 24 bits of precision
+ (/ (pcg-random-bits pcg 24)
+ (coerce (expt 2 24) 'single-float)))
+
+; https://en.wikipedia.org/wiki/Double-precision_floating-point_format
+; Doubles have 53 bits of precision
+(defun pcg-random-double (pcg)
+ (declare (optimize (speed 3) (debug 0) (safety 1))
+ (type pcg pcg))
+ (/ (logior (ash (pcg-random-bits pcg 26) 27)
+ (pcg-random-bits pcg 27))
+ (coerce (expt 2 53) 'double-float)))
+
+(defun pcg-random-range (pcg min max)
+ (+ min (pcg-random-bounded pcg (- max min))))
+
+(defun pcg-random-range-inclusive (pcg min max)
+ (+ min (pcg-random-bounded pcg (1+ (- max min)))))
+
;;;; Scratch
; (spectral)